Step tread frame



FIG. 1 is a perspective view of a step tread frame in an exemplary application;

FIG. 2 is a front perspective view thereof;

FIG. 3 is a front view thereof;

FIG. 4 is a rear view thereof;

FIG. 5 is a top view thereof;

FIG. 6 is a bottom view thereof;

FIG. 7 is a right side view thereof;

FIG. 8 is a left side view thereof; and,

FIG. 9 is a rear perspective view thereof.

The broken lines in FIG. 1 depict environmental subject matter and form no part of the claimed design. 

CLAIM The ornamental design for a step tread frame, as shown and described. 